1. Field of the Invention
The present invention relates to a magnetic transfer apparatus designed to establish a servo region on a magnetic recording medium such as a magnetic disk, for example. The servo region serves to define recording tracks on the magnetic recording medium in a magnetic storage device such as a hard disk drive (HDD), for example.
2. Description of the Prior Art
A preamble region, a servo mark region and a servo data region are in this sequence defined over a servo region on a magnetic recording disk. The preamble region includes alternate positive and negative magnetic poles equally spaced in the circumferential direction. The servo data region includes magnetic poles arranged in accordance with a predetermined pattern varying in the radial direction. A synchronization signal can be obtained in the HDD based on the magnetic information derived from the preamble region. A head is positioned right above a recording track at a higher accuracy based on the magnetic information derived from the servo data region.
When the magnetic poles are to be established on a magnetic recording disk, a blank magnetic disk is set in a magnetic transfer apparatus. A master medium is superposed on the blank magnetic disk in the magnetic transfer apparatus. Magnetic pieces and non-magnetic pieces are alternately arranged in the master medium in accordance with the arrangement of the magnetic poles. When a magnetic field is applied to the master medium in a set direction, leakage of magnetic flux is induced between the adjacent magnetic pieces. This leaked magnetic flux serves to establish magnetization in the magnetic disk.
No magnetic pieces are formed in the master medium at a position corresponding to the servo mark region of the magnetic recording disk. A larger non-magnetic space is defined between the magnetic pieces corresponding to the preamble region and the magnetic pieces corresponding to the servo data region. Leakage of a weak magnetic field is thus induced between the magnetic pieces across the non-magnetic space. The leaked weak magnetic field acts on the servo mark region on the magnetic disk, so that the weak magnetic pole will be established in the servo mark region adjacent the servo data region. Such a weak magnetic pole has a polarity different from that of the first magnetic pole of the servo data region and the intensity smaller than that of the first magnetic pole. This weak magnetic pole is often mistaken for the first magnetic pole of the servo data region. This mistake will disturb the servo control of the head. The head cannot keep following recording tracks on the magnetic disk.